On 2015/11/18 3:19, Robert Haas wrote:
On Thu, Nov 12, 2015 at 12:54 AM, Etsuro Fujita
<fujita.ets...@lab.ntt.co.jp> wrote:
Really? I think there would be not a little burden on an FDW author; when
postgres_fdw delegates to the subplan to the remote server, for example, it
would need to create a remote join query by looking at tuples possibly
fetched and stored in estate->es_epqTuple[], send the query and receive the
result during the callback routine. Furthermore, what I'm most concerned
about is that wouldn't be efficient. So, my question about that approach is
whether FDWs really do some thing like that during the callback routine,
instead of performing a secondary join plan locally. As I said before, I
know that KaiGai-san considers that that approach would be useful for custom
joins. But I see zero evidence that there is a good use-case for an FDW.
It could do that. But it could also just invoke a subplan as you are
proposing. Or at least, I think we should set it up so that such a
thing is possible. In which case I don't see the problem.
I suppose you (and KaiGai-san) are probably right, but I really fail to
see it actually doing that.
Best regards,
Etsuro Fujita
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
